1. Field
Exemplary embodiments of the present invention relate to a method and system for testing a semiconductor device.
2. Description of the Related Art
As the integration degree of semiconductor devices including semiconductor memory devices increases rapidly, a semiconductor device may be provided with more than thousands of unit cells. The semiconductor device may not perform its whole operation even due to one defective cell among thousands of unit cells. However, it is quite inefficient in terms of production yield to discard the semiconductor device because of the failure occurring in a few unit cells. Here, a unit cell means a basic unit for performing an essential function of the semiconductor device. For example, a memory cell may operate as the unit cell in a semiconductor memory device and a processor may be the unit cell of a Central Processing Unit (CPU).
To prevent the semiconductor device from being discarded as described above, a variety of techniques have been developed and applied to the semiconductor device. For instance, a semiconductor memory device includes redundancy cells together with memory cells. Even if some of the memory cells are defective, the semiconductor memory device can be used by repairing them with the redundancy cells. Taking an example of the method of repairing a defective memory cells using a redundancy cell, a spare row unit and a spare column unit are prepared for each predetermined cell array and a row unit or a column unit including the defective memory cell is replaced with the spare row or column unit.
After the processing of manufacturing a wafer is completed, a defective memory cell is selected out through a test. Then, a program for changing the address of the defective memory cell with the address of a spare cell is executed in an internal circuit. Therefore, when the semiconductor device is actually used and the address signal corresponding to a defective memory cell line is inputted, the address signal is changed with the address signal of a spare line. In this way, although some memory cells of a semiconductor device are turned out to have a fault, the entire semiconductor device may be prevented from being discarded.
The above method of using a redundancy cell is widely used but it may increase a chip area because the memory device should include memory cells more than the number of memory cells needed for their essential functions, e.g., the data storage. Therefore, other methods for repairing the defective cells of a semiconductor device are being developed.
The method of replacing a defective cell with a redundancy cell may be performed by using diverse kinds of fuses. Also, the semiconductor device may prevent its operation characteristics from being degraded due to temperature and process by using diverse kinds of fuses.
Meanwhile, the test of a semiconductor device may be performed based on the specification which defines general operation characteristics of the semiconductor device. Semiconductor devices may be designed to have characteristics better than those of the specification. Therefore, the semiconductor memory device may be tested based on diverse operation characteristics including its general operation characteristics by using diverse kinds of fuses.